Laser diodes have been used as a light source in optical communications, laser printers and in compact laser disc players. Several manufacturers, including Lytel and Toshiba, currently produce laser diodes. These commercial products usually comprise a laser diode encapsulated in a "can" having a window disposed in the optical path of the light emitted from the laser diode, and electrical leads protruding from the can. A typical model is the TOLD 9200 Visible Laser Diode, sold by Toshiba America, Inc.
Currently available laser diode packages, however, have been inadequate in terms of their ability to collimate the optical output of the laser diode. Also, the optical elements used in combination with laser diodes to shape the light beam from an elliptical pattern to a circular pattern, i.e., circularizing the emitted light, are complicated and expensive. No means have heretofore been provided for collimating and circularizing the laser diode output while compensating for wavelength shifts of the laser diode. Further, the optical elements used with prior art laser diodes cause a portion of the emitted light to reflect back into the active cavity of the laser diode, disrupting stable performance. Finally, the laser diode and its associated optical elements form a bulky, complex and costly package.
U.S. Pat. No. 4,779,943 to Tatsuno, et al. discloses an optical system which comprises a laser diode and a holographic lens, wherein the optical system is purportedly reduced in weight and size and is simple in design compared to conventional systems consisting of a coupling lens and a cylindrical lens. However, the disclosed hologram lens is a discrete element; it is physically separate from the laser diode. The disclosed apparatus does not contemplate a connector for coupling an optical fiber thereto, nor does it disclose or suggest isolating the laser diode from interfering reflected light.